1. Field of the Invention
This invention relates to a press-in contact and more particularly to a press-in contact which is ideally suited for use in a battery pack which may be used on cellular telephones, two-way radios, etc.
2. Description of the Related Art
Battery packs for cellular telephones, two-way radios, and other equipment requiring a battery pack normally are encased in a plastic housing with the outer surface of the plastic housing of the battery pack normally including a plurality of charging contacts positioned in the outer wall of the plastic housing which enable the battery pack to be conveniently recharged. The inside surface of the battery pack usually contains two or more contacts positioned therein to enable the battery pack to be interfaced with the circuit of the cellular telephone, two-way radio, etc.
The battery pack is used as a means of providing a power source for thousands of different types of wireless devices. Along with the many fundamental components of a multi-cell battery pack, such as battery cells, circuitry, and plastic housing, contacts are used as a mechanically robust interface between the internal electric circuit of a battery pack with the device it powers and/or the charger that restores the electrical capacity of the battery pack.
A large arena of wireless devices includes cellular telephones and land mobile radios or two-way radios. Some of the trends for these devices are to reduce the size and weight of their battery pack power source. The greatest pressure from the customer in reducing the size is placed upon the thickness perimeter of the battery pack. A slimmer design provides two advantages. The first advantage is a more appealing product to the consumer and the second advantage is that additional circuitry can be added to the handset, which can be used to increase the number of features and the performance characteristics. In designing a contact, the requirements must include: (1) a contact that improves the production assembly process; (2) a very slim profile to minimize plastic thickness of the housing as well as overall battery pack thickness; (3) achieves a minimal mechanical push-out force of the contact from the plastic housing; and (4) provides a watertight seal.
Press-in contact designs are currently used in many applications. To the best of applicant""s knowledge, the current press-in contact designs are only able to achieve two of the four desired performance characteristics, that is a mean push-out force requirement and watertight sealing. The disadvantages of former designs are the height or clearance required for the contact and the assembly process being very inefficient in some applications and impossible in others.
A press-in contact is disclosed which is ideally suited for use with a battery pack wherein battery cells are enclosed in a plastic housing having inner and outer walls. The outer wall of the plastic housing has a plurality of circular openings formed therein which extend therethrough. A flexible circuit having inner and outer surfaces is positioned at the inner surface of the outer wall member and has a plurality of circular openings formed therein which register with the circular openings in the outer wall of the plastic housing. The flexible circuit is provided with a circuit trace on its inner surface. Each of the openings in the flexible circuit interrupts the circuit trace on the flexible circuit. A metal tab extends across each of the openings in the flexible circuit which is electrically connected to the circuit trace for electrically connecting the otherwise interrupted circuit trace at the opening. A press-in charging contact is positioned in each of the openings in the outer wall of the plastic housing with the inner ends of the press-in charging contacts being electrically connected to the tabs through the openings formed in the flexible contact. A plurality of battery cells are positioned adjacent to the flexible circuit so as to be in electrical contact with the tabs and the flexible circuit. The inner wall of the plastic housing also has a plurality of circular openings formed therein having a press-in circuit contact positioned therein. The inner ends of the press-in circuit contacts are electrically connected to the flexible circuit.
A primary objective of the new contact of this invention is the use of a spot-welding process to connect a pre-inserted contact to the flexible board and at the same time reduce the component/material count to achieve the same performance and specific functional requirements of previous designs.
Additional objectives include optimizing the design to be as thin as possible while achieving a watertight seal and a minimum push-out separation force while allowing optimal ease of manufacturing assembly.